PURPOSE: To provide a ductless air supply system on rearside of ceiling for house which gives no discomfort to a person in a room by airstream from an air supply port, contributes to an elimination of temperature difference between an upper layer airstream and a lower layer airstream in the room, and also can be manufactured at a relatively low cost and installed easily.

CONSTITUTION: A ceiling rearside structure having an air supply duct function in a space on the rearside of a ceiling is made of a ceiling forming member 2. Or, a fitting of the peripheral edge 3 of the ceiling and/or the peripheral edge of a ceiling illuminator 4 is formed to be hollow in the cross section, pierced with a plurality of distributed small holes and given with a duct function, so that, air supply can be carried out from all over the periphery.